This invention relates to hose, and more particularly relates to long length hose, and to a method and apparatus for making it. The invention is especially concerned with hose which can be used in cryogenic conditions.
Typical applications for hose involve the pumping of fluids from a fluid reservoir under pressure. Examples include supplying of domestic heating oil or LPG to a boiler; transporting produced oilfield liquids and/or gases from a fixed or floating production platform to the cargo hold of a ship, or from a ship cargo hold to a land-based storage unit; delivering of fuel to racing cars, especially during refueling in formula 1; and conveying corrosive fluids, such as sulphuric acid.
It is well known to use hose for the transport of fluids, such as liquefied gases, at low temperature. Such hose is commonly used to transport liquefied gases such as liquefied natural gas (LNG) and liquefied propane gas (LPG).
Many applications of hose require the hose to be supported along its length. This especially applies to the transport of the produced liquids and/or gases mentioned above. Without additional support, conventional hose is often incapable of supporting its own weight, or the weight of the fluid contained therein.
Three main types of hose exist that are used for large bore applications for transferring fluids at elevated pressure (e.g. at least 2 barg). These are:
1. Rubber (rubber wraps vulcanised to form the hose body).
2. Bellows (convoluted steel tube).
3. Composite (films and fabrics between two helical wires).
The present invention is directed to composite hoses.
Rubber hoses differ from composite and bellows hose in that they do not have a steel component on the inner surface.
Rubber hoses are typically manufactured by wrapping numerous layers of rubber materials and some steel and fabric layers around a mandrel coated with a release agent. Some Rubber Hoses use an extruded rubber inner liner on a mandrel as the innermost layer and then wrap after that. Other rubber hoses include an interlocked carcass inside the liner, for collapse resistance. The complete structure is then vulcanised thus bonding the rubber wraps together. The complete hose assembly, including the end fittings which are also on the mandrel and are wrapped into the hose body structure, is removed from the mandrel by pulling and rotating. The hose and mandrel are supported by a series of rollers during this extraction process. Rubber hoses are typically made in lengths of up to 12 m and bores of up to at least 1.2 m.
In essence, the traditional method of manufacture for the bellows and composite hose is the same as that of a rubber hose. A bellows hose is formed in sections supported on steel mandrel and if insulating or protective layers are required these will be wrapped around the bellows tube. A composite hose is traditionally formed by a steel wire being wound helically onto a steel mandrel followed by a number of film and fabric layers. This is then formed into the hose body by the application of a second helical wire.
Both bellows and composite hoses are widely available in bores of up to 200 mm and in lengths of up to about 30 m. However it is difficult to manufacture and extract a large bore hose, greater than 400 mm, of either of these types in a reasonable length, greater than 10 m, using the traditional manufacturing techniques. This is not the case with rubber hoses as they do not have an inner steel component.
Both bellows and composite hoses are currently manufactured on steel mandrels, which for small diameters works well and is the industry standard; but as the diameter increases the effect of friction is increased dramatically. The surface area of contact between the hose and the mandrel increases linearly with diameter but the weight of the mandrel increases approximately with the square of the diameter. The product of these two factors is the friction between the hose and mandrel as during extraction the weight of the mandrel is taken through the hose.
Other factors affecting the ease of extraction include:
Galling between the steel mandrel and the steel wire.
The coefficient of friction between the two materials.
The weight of the hose.
The use of supporting rollers used to control mandrel deflection.
Attempts to manufacture hoses using the traditional techniques have resulted in hoses that have the required bore but are too short, or have the required bore and length but have been damaged during extraction. It has also been the case that the mandrel has become damaged during extraction and so in an industrial setting this process would be impractical and uneconomic.
Composite hose is described in many prior art documents, including, for example, EP-0076540A1 and WO01/96772. As discussed above, this type of hose is characterised by an inner metallic inner structure which is difficult to remove from the mandrel during the manufacturing process. As a result there is a practical limit on the size of hose which can be produced in the prior art, while at the same time retaining the ability to operate in hostile environments, such as in conditions of low and high temperature; and in marine applications.
GB2303574, DE2948416, JP08336845, JP08011138 and JP03075132 disclose a method of making hose or tubing, but they do not disclose the manufacture of bellows hose.
Bellows hose is exclusively manufactured on a metallic mandrel; the mandrel may consist exclusively of the stainless steel or may be clad with stainless steel. In 2005, a carbon steel mandrel might typically cost about. £25,000 and in its working lifetime it would be capable of being used to manufacture about 25-30 individual hoses. However, there is a problem with carbon steel mandrels, as the metallic inner member of the hose is often made of stainless steel. When such hose is manufactured using a carbon steel mandrel, part of the carbon steel can be transferred to the surface of the stainless steel inner member; this causes a site for corrosion of the inner member, which can lead to rapid failure in extreme environments. For this reason, the mandrel used in the manufacture of bellows hose and composite hose usually has to be made of stainless steel. A stainless steel hose costs three to four times as much as a carbon steel mandrel.